Several investigators have concluded that the waist-to-height ratio is more strongly associated with cardiovascular disease risk factors than is the body mass index (BMI; in kg/m(2)).
We examined the relation of the BMI-for-age z score and waist-to-height ratio to risk factors (lipids, fasting insulin, and blood pressures). We also compared the abilities of these 2 indexes to identify children with adverse risk factors.
Children aged 5-17 y (n=2498) in the Bogalusa Heart Study were evaluated.
As assessed by the ability of the 2 indexes to 1) account for the variability in each risk factor and 2) correctly identify children with adverse values, the predictive abilities of the BMI-for-age z score and waist-to-height ratio were similar. Waist-to-height ratio was slightly better (0.01-0.02 higher R(2) values, P<0.05) in predicting concentrations of total-to-HDL cholesterol ratio and LDL cholesterol, but BMI was slightly better in identifying children with high systolic blood pressure (0.03 higher R(2), P<0.05) in predicting measures of fasting insulin and systolic and diastolic blood pressures. On the basis of an overall index of the 6 risk factors, no difference was observed in the predictive abilities of BMI-for-age and waist-to-height ratio, with areas under the curves of 0.85 and 0.86 (P=0.30) and multiple R(2) values of 0.320 and 0.318 (P=0.79). This similarity likely results from the high intercorrelation (R(2)=0.78) between the 2 indexes.
BMI-for-age and waist-to-height ratio do not differ in their abilities to identify children with adverse risk factors. Although waist-to-height ratio may be preferred because of its simplicity, additional longitudinal data are needed to examine its relation to disease.
"Participants of these studies had diabetes of unknown duration . This makes it difficult to distinguish between the role of weight loss as an innocent bystander reflecting poorly controlled diabetes or as a mediator effectuating the impact of diabetes on death or as an independent risk factor . To deal with this limitation, Carnethon et al. have conducted a study on a sample of participant with newly diagnosed diabetes to examine all-cause, cardiovascular, and noncardiovascular mortality. "
[Show abstract][Hide abstract] ABSTRACT: Background. To reconcile "the obesity paradox," we tested if (1) the contribution of anthropometric measures to mortality was nonlinear and (2) the confounding of hip circumference contributed to the obesity paradox recently observed among diabetic patients. Methods. We analyzed data of diabetic patients attending a community-based prospective, "Tehran lipid and glucose study." In the mortality analysis, anthropometric measures-body mass index (BMI), waist, and hip circumference-were assessed using Cox models incorporating cubic spline functions. Results. During 12 990 person-years follow-up, BMI levels below 27 and those above 40 kg·m(-2) were associated with increased mortality. When we added waist circumference to the BMI in the multivariate-adjusted model, the steepness of BMI-mortality association curve slope for values below 27 kg·m(-2) increased, whereas the steepness of BMI-mortality association curve slope for values above this threshold decreased. Further adjusting the model for hip circumference, the steepness of the slopes of the association curve moved towards null on both extremes and no associations between BMI and all-cause mortality remained. Conclusion. BMI harbors intermixed positive and negative confounding effects on mortality of waist and hip circumference. Failing to control for the confounding effect of hip circumference may stymie unbiased hazard estimation and render conclusions paradoxical.
International Journal of Endocrinology 08/2014; 2014:282089. DOI:10.1155/2014/282089 · 1.95 Impact Factor
"The suggestion that WHtR cut-off may be similar in men and women makes it attractive for the quantification of central obesity in children which otherwise, could be very complex when using age-sex-race specific charts. A WHtR cut-off of 0.5 has been proposed for predicting cardiovascular risk , and its accuracy has been reported in several studies , , . Despite its reported advantages and the ease of computing the WHtR, a suitable WHtR cut-off for populations from Africa has yet to be determined. "
[Show abstract][Hide abstract] ABSTRACT: The proposed waist-to-height ratio (WHtR) cut-off of 0.5 is less optimal for cardiometabolic risk screening in children in many settings. The purpose of this study was to determine the optimal WHtR for children from South Africa, and investigate variations by gender, ethnicity and residence in the achieved value.
Metabolic syndrome (MetS) components were measured in 1272 randomly selected learners, aged 10-16 years, comprising of 446 black Africans, 696 mixed-ancestry and 130 Caucasians. The Youden's index and the closest-top-left (CTL) point approaches were used to derive WHtR cut-offs for diagnosing any two MetS components, excluding the waist circumference.
The two approaches yielded similar cut-off in girls, 0.465 (sensitivity 50.0, specificity 69.5), but two different values in boys, 0.455 (42.9, 88.4) and 0.425 (60.3, 67.7) based on the Youden's index and the CTL point, respectively. Furthermore, WHtR cut-off values derived differed substantially amongst the regions and ethnic groups investigated, whereby the highest cut-off was observed in semi-rural and white children, respectively, Youden's index0.505 (31.6, 87.1) and CTL point 0.475 (44.4, 75.9).
The WHtR cut-off of 0.5 is less accurate for screening cardiovascular risk in South African children. The optimal value in this setting is likely gender and ethnicity-specific and sensitive to urbanization.
PLoS ONE 08/2013; 8(8):e71133. DOI:10.1371/journal.pone.0071133 · 3.23 Impact Factor
"Positive intervention effects were observed for body size outcomes, with significant between-group differences identified for waist circumference at post-intervention (−1.63 cm), and BMI z-score at follow-up (−0.24). Waist circumference  and BMI z-scores  are positively associated with cardiovascular disease risk in children and the changes in waist circumference and BMI z-scores of the magnitudes observed here have previously been reported as sufficient for population health benefit . Thus, the positive effects of the CHANGE! "
[Show abstract][Hide abstract] ABSTRACT: This pragmatic evaluation investigated the effectiveness of the Children's Health, Activity and Nutrition: Get Educated! (CHANGE!) Project, a cluster randomised intervention to promote healthy weight using an educational focus on physical activity and healthy eating.
Participants (n = 318, aged 10--11 years) from 6 Intervention and 6 Comparison schools took part in the 20 weeks intervention between November 2010 and March/April 2011. This consisted of a teacher-led curriculum, learning resources, and homework tasks. Primary outcome measures were waist circumference, body mass index (BMI), and BMI z-scores. Secondary outcomes were objectively-assessed physical activity and sedentary time, and food intake. Outcomes were assessed at baseline, at post-intervention (20 weeks), and at follow-up (30 weeks). Data were analysed using 2-level multi-level modelling (levels: school, student) and adjusted for baseline values of the outcomes and potential confounders. Differences in intervention effect by subgroup (sex, weight status, socio-economic status) were explored using statistical interaction.
Significant between-group effects were observed for waist circumference at post-intervention (beta for intervention effect =-1.63 (95% CI = -2.20, -1.07) cm, p<0.001) and for BMI z-score at follow-up (beta=-0.24 (95% CI = -0.48, -0.003), p=0.04). At follow-up there was also a significant intervention effect for light intensity physical activity (beta=25.97 (95% CI = 8.04, 43.89) min, p=0.01). Interaction analyses revealed that the intervention was most effective for overweight/obese participants (waist circumference: beta=-2.82 (95% CI = -4.06, -1.58) cm, p<0.001), girls (BMI: beta=-0.39 (95% CI = -0.81, 0.03) kg/m2, p=0.07), and participants with higher family socioeconomic status (breakfast consumption: beta=8.82 (95% CI = 6.47, 11.16), p=0.07).
The CHANGE! intervention positively influenced body size outcomes and light physical activity, and most effectively influenced body size outcomes among overweight and obese children and girls. The findings add support for the effectiveness of combined school-based physical activity and nutrition interventions. Additional work is required to test intervention fidelity and the sustained effectiveness of this intervention in the medium and long term.Trial registration: Current Controlled Trials ISRCTN03863885.
BMC Public Health 07/2013; 13(1):626. DOI:10.1186/1471-2458-13-626 · 2.26 Impact Factor
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